Thickness-distribution measurement device and thickness-distribution measurement metho

Abstract

A thickness-distribution measurement device includes a light source; a light detector; and a control device. The light source irradiates a region of an object being conveyed with light, the region extending in a width direction. The light detector detects emitted light that has transmitted through the object. The control device obtains information on a distribution of a relative thickness of the object in the width direction based on a detection result in the light detector. The light detector includes an image sensor and a lens array. The image sensor includes a plurality of pixels arranged in the width direction, and detects an intensity of the emitted light for each pixel. The lens array includes a plurality of lenses having an equal magnification and arranged along the width direction, and collects the emitted light and forms an image of the emitted light on the image sensor.

1 . A thickness-distribution measurement device comprising:
 a conveyor configured to convey an object including a first surface and a second surface in a conveying direction along the first surface and the second surface, the second surface facing opposite to the first surface;   a light source that is disposed at a position facing the second surface of the object, and that is configured to irradiate a region of the object being conveyed with light, the region extending in a width direction intersecting the conveying direction;   a light detector that is disposed at a position facing the first surface of the object, and that is configured to detect emitted light that has transmitted through the object irradiated with the light; and   an arithmetic processor configured to obtain information on a distribution of a relative thickness of the region of the object in the width direction based on a detection result in the light detector,   wherein the light detector includes an image sensor that includes a pixel unit including a plurality of pixels arranged at least in the conveying direction, and that is configured to detect an intensity of the emitted light for each pixel to output image data, and a lens unit that includes a plurality of lenses having an equal magnification and arranged along the width direction, and that is configured to collect the emitted light and forms an image of the emitted light on the pixel unit of the image sensor.   
     
     
         2 . The thickness-distribution measurement device according to  claim 1 ,
 wherein an optical axis of the lens unit is along a normal line to the first surface.   
     
     
         3 . The thickness-distribution measurement device according to  claim 1 ,
 wherein an optical axis of the lens unit is inclined with respect to a normal line to the first surface.   
     
     
         4 . The thickness-distribution measurement device according to  claim 3 ,
 wherein an inclination angle of the optical axis of the lens unit with respect to the normal line is 5° or more and 80° or less.   
     
     
         5 . The thickness-distribution measurement device according to  claim 1 ,
 wherein the image sensor is configured to be able to switch a gain value for amplifying signals output from the plurality of pixels.   
     
     
         6 . The thickness-distribution measurement device according to  claim 5 , further comprising:
 another light source that is disposed at a position facing the first surface, and that is configured to irradiate the region or another region of the object being conveyed with light, the another region extending in the width direction,   wherein the light detector is configured to detect emitted light emitted from the object irradiated with the light by the another light source, and   the gain value of the image sensor when irradiation with the light from the another light source is performed is different from the gain value of the image sensor when irradiation with the light from the light source is performed.   
     
     
         7 . The thickness-distribution measurement device according to  claim 1 , further comprising:
 a thickness measurement unit configured to locally measure an absolute thickness of the object,   wherein the arithmetic processor is configured to correct a measurement value of the relative thickness based on the absolute thickness measured by the thickness measurement unit.   
     
     
         8 . The thickness-distribution measurement device according to  claim 1 ,
 wherein the image sensor is a line scan sensor.   
     
     
         9 . The thickness-distribution measurement device according to  claim 1 ,
 wherein the light detector further includes a first optical filter provided on some pixels among the plurality of pixels of the image sensor, and having a transmission wavelength band centered at a first wavelength, and a second optical filter provided on at least some other pixels among the plurality of pixels of the image sensor, and having a transmission wavelength band centered at a second wavelength different from the first wavelength.   
     
     
         10 . A thickness-distribution measurement method comprising:
 starting to convey an object having a first surface and a second surface in a conveying direction along the first surface and the second surface, the second surface facing opposite to the first surface;   starting to irradiate a region of the object being conveyed with light, the region extending in a width direction intersecting the conveying direction;   starting to detect emitted light that has transmitted through the object irradiated with the light; and   obtaining information on a distribution of a relative thickness of the region of the object in the width direction based on a detection result of the emitted light,   wherein in the starting to detect, an image sensor that includes a pixel unit including a plurality of pixels arranged at least in the width direction, and that detects an intensity of the emitted light for each pixel to output image data, and a lens unit that includes a plurality of lenses having an equal magnification and arranged along the width direction, and that collects the emitted light and forms an image of the emitted light on the pixel unit of the image sensor are used.   
     
     
         11 . The thickness-distribution measurement method according to  claim 10 ,
 wherein an optical axis of the lens unit is along a normal line to the first surface.   
     
     
         12 . The thickness-distribution measurement method according to  claim 10 ,
 wherein an optical axis of the lens unit is inclined with respect to a normal line to the first surface.   
     
     
         13 . The thickness-distribution measurement method according to  claim 12 ,
 wherein an inclination angle of the optical axis of the lens unit with respect to the normal line is 5° or more and 80° or less.   
     
     
         14 . The thickness-distribution measurement method according to  claim 10 ,
 wherein the image sensor is configured to be able to switch a gain value for amplifying signals output from the plurality of pixels.   
     
     
         15 . The thickness-distribution measurement method according to  claim 10 , further comprising:
 locally measuring an absolute thickness of the object,   wherein in the obtaining the information, a measurement value of the relative thickness is corrected based on the absolute thickness measured by the measuring.